In the manufacture and processing of printed circuit boards or other substrates on which electrical components are, or to be, mounted, it is often required that work operations be performed in which components are assembled on the board, or previously assembled components are further processed by testing the components or by permanently securing the previously assembled components to the board. These various work operations result in the application of forces to the board and to the components that may be detrimental. As an example, components are loosely assembled on a board and subsequently staked or riveted. If the board is rigidly held on a support, forces wil be transmitted from the work area to other sections of the board causing damage or dislodgement to other previously assembled components. If the board is constructed of rigid non-metallic material care must be exercised otherwise the work operations will result in chipping or fracturing sections of the board.
Among the numerous types of work holders available are those that are mounted on a sphere constructed of magnetizable material which is supported within a cavity formed in a base. By establishing magnetic flux paths through the base and sphere, the sphere may be rotated in various orientations and then magnetically held in a desired orientation. One such work holder is shown in U.S. Pat. No. 2,993,395 issued July 25, 1961, to D. I. Bohn where a sphere of high permeability material is circumferentially supported on the end of a tube with a portion of the sphere extending into the tube to be further supported by a pedestal-like core. Windings of a coil are positioned about the core, and when energized magnetic flux paths are established through the core, a portion of the sphere, the tube and a metallic bed on which the tube and core are supported. The sphere is thus magnetically locked in position and the tube and core are magnetically held against the bed. A work holder, such as a vise, is mounted on the sphere.
A need still exists for a holding fixture which will permit a workpiece to be rotated 360.degree. in a horizontal plane to position the workpiece in a fabricating, testing or processing station and then permit pivotal movement of the workpiece relative to the horizontal plane while a work operation is being performed. It is desirable that such a fixture utilize permanent magnets rather than electromagnets which may induce spurious a.c. currents that may be detrimental to electronic or semi-conductor devices mounted on the workpiece or in any surrounding test equipment.